1. Field of the Invention
The present invention relates to an oil pressure control system of a six speed automatic transmission which has six forward speeds, a low range, and a reverse speed, and includes three planetary gear sets, two clutches, three brakes, and one one-way clutch.
2. Description of the Background Art
In general, an automatic transmission changes power generated in an engine by using oil pressure to obtain a proper rotation force depending on driving conditions. A typical automatic transmission includes a torque converter, a power train connected to the torque converter, and an oil pressure control system controlling the power train with an oil pressure.
The power train of the automatic transmission includes a planetary gear set which receives power of an engine, changes the power to a proper rotation force, and outputs the force; and a fastening element such as a clutch or a brake which fixes each of rotation elements of the planetary gear set or prevents rotation thereof, or which rotates by power of an engine.
Automatic transmissions typically have either four or five speeds. However, recently, in order to increase gas mileage and performance, six speed automatic transmissions have been developed.